Many recent mobile devices among others, especially foldable mobile phones, have two display panels, or so-called “dual panels.” As an example, FIG. 18 shows a circuit diagram of dual panels 581 comprising a main panel 582 and a subpanel 583.
The main panel 582 contains a TFT (thin film transistor) substrate 584, an opposite substrate 585, and a liquid crystal (LC) layer 594. The TFT substrate 584 is a substrate carrying TFTs 592 thereon. The opposite substrate 585 is placed opposite the TFT substrate 584. The LC 594 is a display medium interposed between the TFT substrate 584 and the opposite substrate 585.
On the TFT substrate 584 are there provided gate bus lines 588 and source bus lines 589. A TFT 592 is formed near each intersection of the gate bus lines 588 and the source bus lines 589. The TFT 592 is connected to the gate bus line 588 at the gate, to the source bus line 589 at the source, and to a pixel electrode at the drain. Voltage is applied across the LC 594 in a pixel between the pixel electrode and an opposite electrode (COM) 593 on the opposite substrate 585. This mechanism applies to every TFT 592 across the panel 582, which enables image displays.
The main panel 582 further contains a gate driver 590 and a source driver 591. Lead wires from the gate driver 590 are connected to the gate bus lines 588. Those from the source driver 591 are connected to the source bus lines 589. The gate driver 590 and the source driver 591 apply gate signal voltages and display data signals to the bus lines respectively.
In contrast, the subpanel 583 contains a TFT substrate 586, an opposite substrate 587, and a liquid crystal (LC) layer 594. The TFT substrate 586 is a substrate carrying TFTs 592 thereon. The opposite substrate 587 is placed opposite the TFT substrate 586. The LC 594 is a display medium interposed between the TFT substrate 586 and the opposite substrate 587.
The subpanel 583 is connected to the main panel 582 through a FPC (flexible printed circuit; not shown) board. By virtue of this structure, gate signal voltages and display data signals are fed from the gate driver 590 and the source driver 591 in the main panel 582 to the bus lines in the subpanel 583 through wiring in the main panel 582 and the FPC board.
On the TFT substrate 586 are there provided gate bus lines 588 and source bus lines 589. A TFT 592 is formed near each intersection of the gate bus lines 588 and the source bus lines 589. The TFT 592 is connected to the gate bus line 588 at the gate, to the source bus line 589 at the source, and to a pixel electrode at the drain. Voltage is applied across the LC 594 in a pixel between the pixel electrode and an opposite electrode (COM) 593 on the opposite substrate 587. This mechanism applies to every TFT 592 across the panel 583, which enables image displays. Both the main panel 582 and the subpanel 583 can thus produce image displays.
Examples of prior art literature disclosing concrete dual panel devices include Japanese published patent applications 2001-067049 (Tokukai 2001-067049; published on Mar. 16, 2001), 2001-282145 (Tokukai 2001-282145; published on Oct. 12, 2001), and 2003-131250 (Tokukai 2003-131250; published on May 8, 2003, corresponding to U.S. Patent Application No. 2004/0246428; published on Dec. 9, 2004).
Tokukai 2001-067049 discloses a foldable mobile communications terminal with dual panels: a first liquid crystal display section (first liquid crystal display) and a second liquid crystal display section (second liquid crystal display). The mobile communications terminal is constructed so that a cover section (folder cover) opens/closes on a main body section. The first liquid crystal display section is provided on a face of the cover section which comes inside when the device is folded. The second liquid crystal display section is provided on another face of the cover section which comes outside when the device is folded. The first and second liquid crystal display sections are driven by one driver disposed on the first liquid crystal display section. The driver's outputs are fed to the second liquid crystal display section through the first liquid crystal display section. The second liquid crystal display section is smaller in display area than the first liquid crystal display section. See Tokukai 2001-067049, FIGS. 4, 5. The second liquid crystal display section shows the time and other rudimentary information. The first liquid crystal display section shows various information. In addition, when the cover section is closed, only the second liquid crystal display section produces displays. When the cover section is open, only the first liquid crystal display section produces displays.
Tokukai 2001-282145 discloses a foldable mobile phone with dual panels: a first liquid crystal display section (internal liquid crystal display section) and a second liquid crystal display section (external liquid crystal display section) similarly to Tokukai 2001-067049. The mobile phone is constructed so that a cover section (upper casing) opens/closes on a main body section (lower casing). The first liquid crystal display section is provided on a face of the cover section which comes inside when the device is folded. The second liquid crystal display section is provided on another face of the cover section which comes outside when the device is folded. The first and second liquid crystal display sections are driven by one driver disposed on the first liquid crystal display section. The driver's outputs are fed to the second liquid crystal display section through the first liquid crystal display section. The second liquid crystal display section is smaller in display area than the first liquid crystal display section. See Tokukai 2001-282145, FIGS. 3, 4. When the cover section is closed, only the second liquid crystal display section produces displays. When the cover section is open, only the first liquid crystal display section produces displays.
Tokukai 2003-131250 discloses a foldable mobile phone with dual panels: a first liquid crystal display section (LCD) and a second liquid crystal display section (LCD) similarly to Tokukai 2001-067049. The mobile phone is constructed so that a cover section (lid) opens/closes on a main body section. The first liquid crystal display section is provided on a face of the cover section which comes inside when the device is folded. The second liquid crystal display section is provided on another face of the cover section which comes outside when the device is folded. The first and second liquid crystal display sections are driven by one driver disposed on the first liquid crystal display section. The driver's outputs are fed to the second liquid crystal display section through the first liquid crystal display section. The second liquid crystal display section is smaller in display area than the first liquid crystal display section. See Tokukai 2003-131250, FIGS. 1, 10. The second liquid crystal display section displays a notice of an incoming call, the time and date, and other simple information. The first liquid crystal display section displays major information.
As detailed above, dual panel displays are widely applied to mobile phone and like mobile devices. Demand exists for low power consumption panels. The conventional devices are, however, short of addressing the issue properly.